1Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.

Abstract

Arg and c-Abl represent the mammalian members of the Abelson family of protein-tyrosine kinases. A novel Arg/Abl-binding protein, ArgBP2, was isolated using a segment of the Arg COOH-terminal domain as bait in the yeast two-hybrid system. ArgBP2 contains three COOH-terminal Src homology 3 domains, a serine/threonine-rich domain, and several potential Abl phosphorylation sites. ArgBP2 associates with and is a substrate of Arg and v-Abl, and is phosphorylated on tyrosine in v-Abl-transformed cells. ArgBP2 is widely expressed in human tissues and extremely abundant in heart. In epithelial cells ArgBP2 is located in stress fibers and the nucleus, similar to the reported localization of c-Abl. In cardiac muscle cells ArgBP2 is located in the Z-disks of sarcomeres. These observations suggest that ArgBP2 functions as an adapter protein to assemble signaling complexes in stress fibers, and that ArgBP2 is a potential link between Abl family kinases and the actin cytoskeleton. In addition, the localization of ArgBP2 to Z-disks suggests that ArgBP2 may influence the contractile or elastic properties of cardiac sarcomeres and that the Z-disk is a target of signal transduction cascades.